Lighting is vital to our modern life. Whether it’s lighting homes, offices, public buildings, providing security or just creating an atmosphere. In fact, about 25% of the energy in a typical building is used for lighting, making it one of the most important energy uses on the planet.
Combined with the extremely low efficiency of incandescent lighting solutions, energy costs are increasing at an alarming rate. It’s easy to see that we’re wasting a lot of the world’s resources and paying a high price for it.
As a result, governments are looking to regulate lighting through new energy efficiency regulations, and new technologies such as LEDs are becoming mainstream, promising to save up to 40% of the energy used for lighting.
However, as designers and consumers begin to seek more energy-efficient and innovative lighting solutions, newer technologies need to be developed to meet current and future market demands. To maximize its potential, smart lighting requires more sophisticated and innovative approaches.
ON Semiconductor is addressing the lighting industry challenges related to efficient power conversion and efficient dimming, while seeking next-generation technologies that offer greater energy efficiency, among other benefits.
The Challenges For Lighting Designers
Strengthened government control and consumer demand have made modern lighting designers increasingly challenging. Agencies such as ENERGY STAR and the European Commission are concerned not only with the energy efficiency of electronic equipment, including lighting, but also with its standby power consumption, which can be a significant source of energy consumption over long periods of time. In smart lighting scenarios, this challenge becomes even more tricky, as the power supply must remain “on” in search of a signal from the controller, thus continuously drawing current. Currently, Energy Star rules allow 0.5W of standby power consumption, but agencies such as the California Energy Commission (CEC) plan to reduce that number to 0.2W by 2019, further escalating the challenge.
As lighting has moved from incandescent to LED technology, the dimming aspect has also changed. More complex pulse-width modulation (PWM) techniques are gradually replacing simple resistive or TRIAC-based dimming, requiring designers to take a different approach.
LEDs are a low voltage technology, which means they cannot be driven directly from mains like incandescent lamps, but instead require a power supply that provides either constant voltage (CV) or constant current (CC) power depending on the LED application. The power supply has a substantial impact on the overall performance and energy efficiency of a lighting solution, and therefore needs to be subject to at least as much scrutiny as the LED itself.
There are many different lighting solutions on the market today, ranging from a few watts to hundreds of watts. Therefore, the design methods of its driving power supply are also varied. At lower power levels (usually below 10W), the single-stage conversion topology is the most popular solution.
As multi-functional solid-state lighting becomes more widely used, LEDs and their associated power supplies are also being squeezed into less space, which means that efficiency is critical so that waste heat generation can be reduced to a minimum. minimum, and can reliably install, operate lighting solutions in small and often confined spaces.
An important reason for the rapid development of LED lighting solutions is the decline in the price of LEDs themselves. As a result, installers and consumers not only expect better performance from LED power supplies in a smaller space, but also expect to see similar price reductions (meaning designers need to reduce component count and reduce overall BoM costs) .
Modern Lighting Power Conversion Method
Lighting in the 25W – 100W range for offices, factories and homes is one of the fast-growing market segments where the two-stage approach is the most common solution. In many applications, a flyback power factor corrector (PFC) is used with a power supply in the form of a step-down DC-DC converter.
This method is especially suitable for solutions with dimming requirements. It also enables easy LED shutdown in standby mode and simple control of multiple LED strings for more complex lighting solutions.
ON Semiconductor recently introduced an integrated solution for this type of application, which enables the design of high-performance lighting power supplies using two IC products and a small number of external components.
The FL7740 is a single-stage CV primary-side regulation (PSR) controller that provides CV regulation (±3%) with built-in dynamic capabilities including fast response time impulse is minimized to within 10% of the output voltage.
The controller supports universal wide-range AC input from 80V AC to 382V AC and is suitable for mains powered applications anywhere in the world. It is capable of delivering up to 100W of power while consuming only 0.15W in standby mode – easily exceeding all regulatory requirements. At the same time, the “continuous on” operation that is critical to smart lighting solutions is also achieved.
The built-in PFC stage is capable of >0.9 at full load with THD <10%. At half load, the optional PF optimizer is used, and the value of 0.9 PF remains the same. This ensures that input interference is kept to a minimum over a wide load range, allowing the FL7740 to be widely used.
This advanced controller includes a series of protection functions critical to the safe operation of lighting systems: overload protection, output diode short protection, sense resistor short/open protection, and VDD and VS overvoltage protection.
The FL7760 step-down (“Buck”) controller operating in continuous current mode (CCM) provides the second stage of conversion. The device operates over a wide voltage input range of 8V to 60V, supports both wide analog and PWM dimming, and consumes only 150µA.
Importantly, the PWM dimming of the FL7760 covers the full output range of 1-100%, although under certain operating conditions, undesirable flicker and audible noise may occur due to the operating frequency of the PWM. The analog dimming range is 5-100%, which is a significant improvement over the prior art compared to the 15-100% that is usually achieved today. In general, analog dimming is favored because it doesn’t have the pitfalls of PWM, and the FL7760 makes it a viable option for the first time.
One of the significant advantages of dimming below the analog threshold of 5% is the FL7760’s ability to combine analog and PWM to provide hybrid dimming that seamlessly combines the two to provide full range dimming without There are flicker and audible noise issues.
Like the FL7740, the FL7760 also provides a variety of protection features, including thermal shutdown and overcurrent protection.
Summarize
As LED lighting is gaining popularity due to its low power consumption, versatility, and inherent compatibility with smart lighting solutions, designers are increasingly demanding performance, especially for operation at low standby power and the ability to provide a wide dimming range.
Semiconductor devices such as ON Semiconductor’s FL7740/FL7760 combination meet these performance challenges and provide a compact, low-component-count solution that provides a state-of-the-art lighting power solution at a very competitive cost.
